I dont think bards need to worry about quelling strikes(2.5 bard was a whole new monster with opening enmity), I don't see summoners needing to worry about quelling strikes, I do think as a blm if you have a bard, for your opener using quelling strikes would be beneficial in the chance you happen to get lucky crits in, 10-14k crits in an opener or 2 lucky ones in can really spin a mob around especially if the tank has not finished his enmity combo. Honestly, it lasts 15 seconds, you probably only need 10 seconds of its cushion so you can pre-pop it before a pull.